The present invention relates to a technique of cleaning a substrate (a wafer) in production of semiconductor devices or the like.
Semiconductor devices for use in networks or digital household electric appliances are being further desired to be sophisticated, multifunctional, and low in power consumption. Accordingly, the trend toward micro-patterning for circuits has been developed, with which micro-sizing of particles has so advanced as to cause reduction in production yield. As a result of this, a cleaning step for the purpose of removing contaminants such as the micro-sized particles and the like is frequently used. As a result of this, 30-40% of the whole of the semiconductor fabrication process is occupied with the cleaning step.
On the other hand, at the time of cleaning as conventionally performed with an ammonia-mixed cleaning agent, damages to a wafer due to the basicity has been getting serious together with the trend toward micro-patterning for circuits. Therefore, alternation with a less damaging one, i.e., a dilute hydrofluoric acid-based cleaning agent is taking place.
With this, problems about the damages to the wafer due to cleaning have been solved; however, problems due to an aspect ratio increased with the trend toward micro-processing in the semiconductor devices have become obvious. In other words, a phenomenon where the pattern causes a collapse when a gas-liquid interface passes through the pattern is brought about after cleaning or rinsing so as to largely reduce the yield, which has become a significant problem.